Enable the hparams plugin

[erzel]

• Motivation for features / changes: Enable the HParams plugin in Tensorboard. HParams allows visualizations of experiments ran for hyperparameter tuning.

• Screenshots of UI changes
  

• Detailed steps to verify changes work correctly (as executed by you)

bazel test //tensorboard/plugins/hparams/...:all
bazel run //tensorboard/plugins/hparams:hparams_demo 
bazel run //tensorboard -- --logdir /tmp/hparams_demo 

and (briefly) verified manually that the plugins works as expected.

[erzel]

@manivaradarajan @GalOshri
Here is the PR for enabling hparams in TB. Please take a look, thanks.

Erez.

[wchargin]

Lovely! Can confirm that running the demo script to generate fresh data
causes the hparams plugin to appear as active, and that the main
features that I know about appear to work as intended. Nice work.

Please change “Enabled” to “Enable” in the pull request title, to follow
standard open-source style (which also happens to be Google style).

Please fill in the appropriate parts of the pull request description
template. In particular, a test plan is required, and at least a
screenshot would be appreciated.

Some usability observations:

• When the dashboard is selected when it is inactive, the backend
  400s. Instead, it should show a nice “no data” message.

• When the backend 400s, this is shown to the user via an alert,
  which is pretty intrusive. Instead, we might want to show a
  paper-dialog—or just display appropriate text in the “no data”
  message.

Are these being tracked anywhere?

One change requested inline, then you should be good to go as long as
the above issues are in some known tracker (preferably public).

[erzel]

I've added tracking of the bugs above to our internal tool since this is where the other bugs are currently logged. We can export all of them as github issues later.

[erzel]

Thanks @wchargin! PTAL.

[wchargin]

Thanks!